The present invention relates to metering dispensers and, more particularly, to an improved dispensing system which is adapted for use in combination with a robot in which a ribbon of high viscosity, high concentration material such as adhesives or sealants can be applied continuously or intermittently to a substrate along a predetermined path.
In FIG. 1, the prior art dispensing system includes a dispensing apparatus 10, a material supply means such as a pressurized tank 12 for holding the material to be applied or dispensed, and a pressurized air tank 14. The dispensing apparatus 10 includes a pneumatically operable valve (not shown) and a nozzle 18 connected thereto. The material to be applied is pumped through a conduit 20 to the dispensing apparatus 10 and the opening of the valve is adjusted by varying the pressure from the air tank 14 so as to maintain the material flow at an appropriate level.
The foregoing arrangement has a number of disadvantages, as follows:
(1) The flow rate of material from the dispenser nozzle is not necessarily proportional to the opening of the valve. Thus the dispenser cannot provide a precise control of the discharge rate;
(2) Bending or elongation of the conduit connecting the pressurised material supply tank and the dispensing apparatus as it moves, will cause an undesirable error or deviation from a predetermined discharge rate;
(3) Refilling the supply tank will necessitate interruption of the dispersion operation, which inconveniences the operator and reduces the efficiency of operation;
(4) When the dispensing apparatus is employed in combination with a robotic system, the material pattern width tends to vary and sometimes increase abruptly as the robot moves, since the robot velocity varies during initial start-up, immediately before making stops and when cornering; and
(5) When it is desired to interrupt the dispersion operation, the dispensing apparatus cannot instantly stop discharging the material from the nozzle despite a rapid closure of the valve.